Can reproduce this on my system.

Steam client version (build number or date): 1769025840
Distribution: EndeavourOS
Opted into Steam client beta?: No
Have you checked for system updates?: yes
Steam Logs: Archive.tar.gz
GPU: AMD Radeon RX 9070 XT

Please describe your issue in as much detail as possible:

Steam client failed to collect the system information from the steam client.

This can only be done from within the Steam Client.

Steps for reproducing this issue:
Create or edit a review
Check the box to "Attach PC Specs to this review"
Select "Add ne PC configuration"

Same issue here when trying to initially save the system configuration directly from the game review box.
Fedora 43 KDE, Steam installed as Flatpak from Flathub, updated to the latest / current stable version.

BUT also a working alternative method:
In the Steam client, go to your 'Account details' (click on your name in the top right, select 'Account details'). In this page, select 'Data & Browsing' in the left side menu. Scroll all the way down and click on the blue box labelled '+ Add This PC'.
This works, you can save your system specs and then also select them when writing a review. I just didn't check if they get attached, but at least there's no more error message if you do it this way around.

This works, you can save your system specs and then also select them when writing a review. I just didn't check if they get attached, but at least there's no more error message if you do it this way around.

I was able to add my PC but after editing some old reviews to check the respective setting to share the specs, nothing is shown.
I can select what specs to add but the review does not address this.

Bazzite with the same problem. The "account details" workaround works.

@Naltarunir not being able to see the specs on the review is another issue, bad design I guess. They only show up when seeing the review in the game's store page.

I checked that too. None of the reviews I left with the checkbox did show my HW.
I did see other reviews with HW specs attached however.

I don't see them from a browser either. The result is also not tied to my login (as in "does not show your own device specs") because this holds true even if I'm visiting as a guest or from a different browser.

@Naltarunir not being able to see the specs on the review is another issue, bad design I guess. They only show up when seeing the review in the game's store page.

Testing the work around on a review i have on a game's storepage actually managed to show my specs but only when i used incognito browser window. didn't show on any other view only the storepage.

Is there a log of some sort we could generate/collect to help troubleshoot this issue? Seeing same thing on Manjaro (Arch)